[PATCH net] net: ethernet: mtk_eth_soc: fix uninitialized variable

[kernel test robot]

Hi Daniel,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Daniel-Golle/net-ethernet-mtk_eth_soc-fix-uninitialized-variable/20230907-234141
base:   net/main
patch link:    https://lore.kernel.org/r/51d1ae238aecde07b2b4fe02cdab0dc87287cd96.1694099183.git.daniel%40makrotopia.org
patch subject: [PATCH net] net: ethernet: mtk_eth_soc: fix uninitialized variable
config: alpha-allyesconfig (https://download.01.org/0day-ci/archive/20230908/202309080027.e4rJ0o2x-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230908/202309080027.e4rJ0o2x-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309080027.e4rJ0o2x-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/uapi/linux/posix_types.h:5,
                    from include/uapi/linux/types.h:14,
                    from include/linux/types.h:6,
                    from include/linux/of.h:14,
                    from drivers/net/ethernet/mediatek/mtk_eth_soc.c:9:
   drivers/net/ethernet/mediatek/mtk_eth_soc.c: In function 'mtk_poll_rx':
>> include/linux/stddef.h:8:14: warning: initialization of 'dma_addr_t' {aka 'long long unsigned int'} from 'void *' makes integer from pointer without a cast [-Wint-conversion]
       8 | #define NULL ((void *)0)
         |              ^
   drivers/net/ethernet/mediatek/mtk_eth_soc.c:2008:31: note: in expansion of macro 'NULL'
    2008 |         dma_addr_t dma_addr = NULL;
         |                               ^~~~


vim +8 include/linux/stddef.h

^1da177e4c3f41 Linus Torvalds   2005-04-16  6  
^1da177e4c3f41 Linus Torvalds   2005-04-16  7  #undef NULL
^1da177e4c3f41 Linus Torvalds   2005-04-16 @8  #define NULL ((void *)0)
6e218287432472 Richard Knutsson 2006-09-30  9  

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0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki